condensing drive

A gasflood process in which an injection gas enriched with components of intermediate molecular weight, for example butane, is injected into a reservoir to achieve multiple-contact miscibility. Upon contact with the oil, intermediate molecular-weight hydrocarbons transfer from the injected gas phase into the oil phase, a process in which those components are said to condense into the oil.
Formation of miscibility may require several contacts between fresh enriched gas and the oil containing condensed components. If the reservoir oil becomes sufficiently enriched with these components that miscibility results between the injection gas and the enriched oil, then the enriched gas and oil have multiple-contact miscibility.
A backward multiple-contact test is a laboratory evaluation of a condensing drive process. In the field, both forward- and backward-contact processes can occur during a given gasflood.